1. Field of the Invention
The present invention relates to aminoketone derivatives and their salts, which are of value as medicinals and particularly as brain function ameliorating agents which may be indicated in conditions such as senile dementia and Alzheimer's disease.
With the proportion of elderly people in the total population being on a steady increase, a number of compounds claimed to have brain function ameliorating activity have been introduced. Among such compounds, the cholinesterase inhibitor physostigmine has been found to possess a brain function ameliorating action.
Physostigmine, however, has several drawbacks, among which are a short duration of action and a high toxicity potential.
The object of the present invention is to provide a cholinesterase inhibitor composition which is more potent, longer-acting and less toxic than any compound hitherto known to have brain function improving activity.
In (1) Journal of Medicinal Chemistry 32, 105 (1989) (as a by-product of reaction), (2) Japanese Patent Application KOKAI No. 95267/1975 (as an intermediate compound for synthesis), (3) Japanese Patent Application KOKAI No. 20134/1972 (as central nervous system depressant etc.) and (4) U.S. Pat. No. 3,197,507 (as central nervous system depressant etc.), there are disclosed the following compounds (1)-(4), respectively, but there is no mention of cholinesterase inhibiting activity and a brain function ameliorating agent. ##STR2##
The inventors of the present invention explored a class of compounds which could be of value as brain function improving agents having anticholinesterase activity and found that an aminoketone derivative which has the formula (I') ##STR3## wherein ring A' designates a five through eight-membered cyclic group which may be substituted and may contain one or two hetero atom(s) of O, S, N, as the ring-constituents; R.sup.1' means a hydrogen atom or a hydrocarbon residue which may be substituted; R.sup.2' means a hydrogen atom or a lower alkyl group; R.sup.3' means an aromatic group which may be substituted; R.sup.4' means a hydrogen atom, a lower alkyl group or an aromatic group which may be substituted; n' means an integer of 2 to 7, or a physiologically acceptable salt thereof has excellent brain function ameliorating activity. The inventors further succeeded in the creation of novel compounds, which have not been described in any literatures, among the compounds of the formula (I'), and accomplished the present invention.